Subzero: Use register availability during lowering to improve the code.

src/IceRegAlloc.h

 //===- subzero/src/IceRegAlloc.h - Linear-scan reg. allocation --*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 44 matching lines @@
     bool AllowOverlap = false;
     llvm::SmallBitVector RegMask;
     llvm::SmallBitVector Free;
     llvm::SmallBitVector PrecoloredUnhandledMask; // Note: only used for dumping
     llvm::SmallVector<RegWeight, REGS_SIZE> Weights;
   };
 
   bool livenessValidateIntervals(const DefUseErrorList &DefsWithoutUses,
                                  const DefUseErrorList &UsesBeforeDefs,
                                  const CfgVector<InstNumberT> &LRBegin,
-                                 const CfgVector<InstNumberT> &LREnd);
+                                 const CfgVector<InstNumberT> &LREnd) const;
   void initForGlobal();
   void initForInfOnly();
   /// Move an item from the From set to the To set. From[Index] is pushed onto
   /// the end of To[], then the item is efficiently removed from From[] by
   /// effectively swapping it with the last item in From[] and then popping it
   /// from the back. As such, the caller is best off iterating over From[] in
   /// reverse order to avoid the need for special handling of the iterator.
   void moveItem(UnorderedRanges &From, SizeT Index, UnorderedRanges &To) {
     To.push_back(From[Index]);
     From[Index] = From.back();
@@ skipping 43 matching lines @@
   llvm::SmallVector<const llvm::SmallBitVector *, REGS_SIZE> RegAliases;
   bool FindPreference = false;
   bool FindOverlap = false;
 
   const bool Verbose;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEREGALLOC_H